Selective and sensitive fluorescence imaging reveals microenvironment-dependent behavior of NO modulators in the endothelial system

Nitric oxide (NO) is a second messenger playing crucial roles in the signaling of a variety of cellular functions. Due to its pathophysiological significance, various NO modulators have been developed to explore NO pathways and some have been used as therapies. These modulators are often used directly to observe pharmacological effects in cell lines, but their actual effect on intracellular NO level is seldom analyzed. Herein, facilitated by a selective and sensitive fluorescence probe, we observed that some NO modulators displayed unexpected behaviors with both NO scavenger carboxy-PTIO and endothelial nitric oxide synthase (eNOS) inhibitor N(ω)-nitro-l-arginine methyl ester (l-NAME) failing to decrease intracellular free NO level in EA. hy926 cells while NO donor diethylamine-NONOate (DEA·NONOate) and eNOS activator calcimycin (A23187) failing to increase free NO level in human umbilical vein endothelial cell line (HUV-EC-C), although the reagents were confirmed to work normally in the primary human umbilical vein endothelial cells (primary HUVECs) and RAW 264.7 macrophage cells. Further research suggested that these unusual behaviors might be attributed to the cellular microenvironments including both the NO synthase (NOS) level and the endogenous glutathione (GSH) level. Genetically manipulating eNOS level in both cells restores the expected response, while decreasing GSH level restores the ability of DEA·NONOate to increase NO level in HUV-EC-C. These results reveal that the cellular microenvironment has a profound impact on pharmacological effect. Our study suggests GSH as a reservoir for NO in live cells and highlights the value of chemical probes as valuable tools to reveal microenvironment-dependent pharmacological effects.

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An imaging based method for evaluating the efficacy of NO modulators in live cells was developed.

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Some NO modulators were observed yielding unexpected effects on cellular NO levels in some endothelial cell lines.

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Further study unveiled intracellular microenvironments have profound effects on the efficacy of NO modulators in live cells.

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This result highlights the pitfall of the specific cellular microenvironments on drug efficacy.

Risk Factors for Acute Mesenteric Ischemia in Critically Ill Burns Patients-A Matched Case-Control Study

OBJECTIVE

Burn-induced shock can lead to tissue hypoperfusion, including the gut. We performed this study to describe burn patients at risk of acute mesenteric ischemia (AMI) with the aim to identify potential modifiable risk factors.

METHODS

Retrospective case-control study including adult severely burned patients between August 2012 and March 2017. Patients who developed AMI were matched to severely burned patients without AMI at a ratio of 1:3 (same year of admission, Abbreviated Burn Severity Index [ABSI], and Simplified Acute Physiology Score II [SAPSII]). Univariate and multiple regression analyses were performed.

RESULTS

Of 282 severely burned patients, 15 (5%) were diagnosed with AMI. In the AMI group, patients had a median (interquartile range) total body surface area (TBSA), SAPSII, and ABSI of 55 (25-63)%, 53 (39-70), and 11 (8-13), respectively. The AMI mechanism in all patients was nonocclusive. Decreased cardiac index within the first 24 h (H24 CI), higher sequential organ failure assessment score on day 1 (D1 SOFA), and hydroxocobalamin use were associated with AMI. Odds ratios were 0.18 (95% confidence interval [CI], 0.03-0.94), 1.6 (95% CI, 1.2-2.1), and 4.6 (95% CI, 1.3-15.9), respectively, after matching. Multiple regression analysis showed that only decreased H24 CI and higher D1 SOFA were independently associated with AMI. Ninety-day mortality was higher in the AMI group (93% vs. 46% [P = 0.001]).

CONCLUSIONS

Burns patients with initial low cardiac output and early multiple organ dysfunction are at high risk of nonocclusive AMI.

Hemodynamic coherence in patients with burns

Burn shock is characterized by profound hemodynamic alterations mainly associated with rapid loss of intravascular volume related to severe capillary leak. Thus, fluid resuscitation conventionally based on macrocirculatory targets is considered as a corner stone of initial management of patients with burns. Nonetheless, traditional markers such as blood pressure, urinary output, and cardiac output are helpful but do not sufficiently reflect the adequacy of perfusion and oxygenation at the microcirculatory level. Microcirculatory alterations have been identified in patients with severe burns even when macrocirculatory variables are within therapeutic goals. In this review, we discuss the pathophysiology of the microvascular alterations in burn shock, its coherence with macrocirculatory physiologic variables, and potential future implications for the treatment of burn shock.